Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**Skyblast72****Member**- Registered: 2012-09-30
- Posts: 16

6/16=.38

6 possible outcomes 16 total outcomes is how I figured it. .38 is one of the answer choices.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,410

What question are you working on?

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

Offline

**Skyblast72****Member**- Registered: 2012-09-30
- Posts: 16

4th one with tree diagram

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,410

4)

A school club consist of 20 male students and 15 female students. If 4 students are selected to represent the club in the student government, what is the probability 2 will be female and 2 will be male?

That is a commitee problem and there is a formula for those.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

Offline

**Skyblast72****Member**- Registered: 2012-09-30
- Posts: 16

Ok I used the diagram. I never know when to use which formula!!! I'll just be happy to pass this class, it's so frustrating. Wish my mind worked like yours!!

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,410

Hold on, there are many incorrect assumptions in those statements.

I'll just be happy to pass this class, it's so frustrating.

Math is hard. Get that sunk in first. It takes a lot of effort and practice. I have been doing it for 100 years and still am lost.

Wish my mind worked like yours!!

What good would that do you? Then there would be two dummies on this forum. Stick with your own mind you are better off. Check this out:

Who says I am right? In mathematics we prove things for ourselves. We do not ever take anyone's word no matter how great.

There are 4 ways of doing things. The right way, the wrong way, my way and everyone else's way.

If you want I will give you my solution. You will have to decide which one you want. See post #4 for my way.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.** **A number by itself is useful, but it is far more useful to know how accurate or certain that number is.**

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,503

Hi Skyblast72 and bobbym,

I think 6/16 is correct. What are you getting please, bobbym (+ method) ?

Wait a mo. Did you get 0.0635...

I may have made an error here. Whoops.

My re-calc is 0.3810

If bobbym agrees I'll have to explain how to modify the tree diagram, (it still works but the probabilities are more tricky to work out)

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 102,410

Hi Bob;

I am using a committee problem template.

http://www.analyzemath.com/statistics/s … ity_3.html

problem #2

http://www.algebra.com/algebra/homework … 52126.html

The ordinary tree does not contain the structure of a committee.

See post #4 for the answer. Simpler to use the formula. The answer is:

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,503

Thanks. yes, that's my answer too. My tree is still ok but the probabilities on the branches are not equal.

Skyblast72: Sorry. Revised diagram below.

I had disregarded the number of males and females available.

There are six outcomes but the probability of each is not 1/16.

Let's say the first chosen is a male. There are 20 to choose from out of 35 students altogether. So P(M) = 20/35.

Now suppose the next chosen is also male. There are 19 to choose from out of 34 students so P(M) = 19/34

Then if you were to choose a female next that would be P(F) = 15/33

And the last female would be P(F) = 15/32

Thus P(MMFF in that order) = (20x19x15x14)/(35x34x33x32)

If you choose in a different order you get the same calculation but the numbers come in a different order.

eg P(MFMF) = 20/35 x 15/34 x 19/33 x 14/32

All six outcomes have this same calculation so P(two Ms and two Fs in any order) =

Hope I haven't confused you with my earlier post.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline